The overall goal of this collaborative Fast-Track project is clinical development of a novel 18F PET tracer for molecular imaging of receptors for vascular endothelial growth factor (VEGFR). This receptor is the major anti-angiogenic drug target in oncology patients. Critically, VEGFR prevalence decreases when VEGF/VEGFR anti-angiogenic inhibitors work, and increases when these drugs stop working. These findings provide a rationale for VEGFR imaging for image-guided anti-angiogenic therapy. To provide for high selectivity, specificity, and VEGFR-mediated intracellular accumulation, the 18F PET tracer will be targeted by VEGFR ligand, scVEGF. The protein will be site-specifically derivatized with a strained alkyne for copper-free click- chemistry radiolabeling with 18F-PEG(4)-azide. In Phase I of this project we will select the lead scVEGF/Alkyne conjugate, optimize conditions for 18F radiolabeling, and validate the use of lead tracer for monitoring anti- angiogenic therapy in a murine model of triple negative breast cancer. In Phase II we will produce cGMP grade conjugate, undertake FDA-required toxicology and dosimetry studies, and proceed to Phase I clinical trials in healthy volunteers.